a112d17438
Add an option to hhvm to 503 requests if they have been sitting on the select queue for too long. Threshold is configurable via runtime option and default off for now. This works with either LIFO or FIFO mode. Basicallly before worker dequeues a request, it peek at the beginning of queue to see if it's expired. If so, it takes that off the queue and aborts the request without executing anything.